My dog Sammy’s water bowl buzzed with activity yesterday morning. When I went to fill it with fresh water, I noticed a honeybee had fallen in. In its attempt to free itself from the sticky surface tension of the water’s surface, the bee’s wingbeats created a spectacular pattern of repeating waves on the water’s surface. I went and got the camera, took a few photos and then offered a blade of grass to the bee, which it quickly grabbed with its forelegs, allowing me to lift it from the bowl. The bee that lived got me thinking about waves and light. For that I’m as thankful as he was.
A honeybee’s wings beat about 200 times per second or in scientific terms 200 Hertz (200 cycles per second). Since the human ear can pick up sounds as low as 20 Hertz, we can easily hear a bee buzz by. Mosquitos beat their wings at a higher frequency – some 600 Hertz – which is why they sound higher pitched to our ears. The more beats per second, the higher the frequency and the shriller the sound.
Light like sound also is made of waves, but while sound waves are compressions (peaks) and relaxations (troughs) of air, light is an electromagnetic wave composed of alternating electrical and magnetic fields. Light doesn’t need a medium for travel. It zooms through a vacuum as happily as through water, glass or air. Sound requires a medium, either air, liquid or solid, for it to register in your ear. We don’t often think of it, but sound travels very well through solids. I remember as a kid putting my ear to the iron rails to anticipate a train coming before I could see it. Then we got our pennies ready, so the train could flatten them into little pancakes.
Despite their differences, sound and light still both waves that behave like waves of water with repeating peaks and troughs. Like the honeybee’s wings stroking the water, light “beats” or has a frequency, too that depends upon its color. If you think a mosquito is high-pitched, light will blow you away. Red light has a frequency of 430 trillion Hertz and and violet light 750 trillion Hertz. That’s right – when you shine a flashlight, 750 trillion wave crests pass through a given point in space every second. That’s some buzz!
And since visible light is only a small part of the entire light or electromagnetic spectrum, those numbers go much higher as we move toward ultraviolet, X-rays and gamma rays. The higher the frequency the light, the more energy it packs, too. That’s why ultraviolet light can burn and damage skin. Light that vibrates at fewer cycles per second than visible light packs less punch. Infrared light, which we sense as heat, as well as radio waves are its most familiar forms.
While we’re on the topic of light, our big, bright sun let loose a powerful M-class flare early this morning. It was centered in the large sunspot region numbered 1283 in the photo above. Since this spray of sub-atomic particles from the flare is directed toward Earth, auroras are a possibility in the nights ahead. I’ll be monitoring solar weather forecasts to let you know if anything might materialize.